Control valves are commonly used to control the fluid flow through a pipe. As known to those skilled in the art, a control valve regulates the rate of fluid flow as the position of the valve plug within the control valve is changed by an actuator. Two important features of a control valve, such as a globe valve, are that it must contain the fluid without external leakage and it must be capable of withstanding the temperature influences of the process. Typical globe valves are used in numerous applications ranging from simple level control to boiler feedwater systems and superheated bypass applications. Globe valves characteristically have a linear moving valve plug contained within a globular-shaped cavity to control flow. Due to the broad application of globe valves, there are a large variety of styles and sizes. Generally, large globe valves are defined as having a flow control orifice or port greater than 6-inches in diameter and are known to suffer from seal failures.
For example, large port globe valves are frequently used in process applications encountering temperatures in excess 300 degrees Fahrenheit and pressure drops exceeding 150 psi. These extreme operating conditions create valve assembly leakage problems due to differences in the thermal expansion of materials of construction and subsequent relaxation of typical gaskets and seals. Leaks are addressed in conventional globe valve assemblies by applying excessive stress or loading in the bonnet bolting. As known to those skilled in the art, excessive bonnet bolting stress increases cost by requiring special materials of construction and increases the probability of failure of the valve in extreme operating conditions by increasing physical stress across the valve bonnet assembly.